Shallow, low-energy temperate-water carbonates from the Cenozoic Murray Basin, South Australia

Shallow, low-energy, temperate-water carbonates of the Murray Supergroup record broad scale, epeiric ramp sedimentation in the intracratonic Murray Basin of South Australia during mid-Cenozoic time. This succession forms a critical link between the few low-energy, temperate-water carbonates of the modern and the many vast epeiric sea deposits of the ancient rock record.; Sediments occur in four associations: (1) clay facies; (2) molluscan facies; (3) echinoidal-bryozoan facies; and (4) large foraminiferan-bryozoan facies. Each association represents deposition in progressively deeper water, more oligotrophic, and higher energy environments. Wet, cool climatic conditions of the late Oligocene to early Miocene resulted in basin wide contraction of the trophic resource continuum and the development of heterozoan, infaunal facies in relatively turbid waters. Gradual warming and drying during the middle Miocene lowered trophic resource levels, allowing foraminifer-photozoan facies, bryozoan, and seagrass meadows to flourish in less turbid waters across the ramp.; Stratigraphic packaging reflects transgressive-regressive cyclicity in response to eustatic forcing. Changes in the carbonate factory, as a response to middle Miocene climate change, led to enhanced carbonate productivity, increased accumulation rates (>200%), and expanded stratigraphic completeness, thus significantly altering packaging style.; A decimetre-scale subtidal cycle forms the basic depositional unit in all facies. Integrated vertical pattern recognition reveals a consistent deepening-upward trend formed under short-term eustatic fluctuation. These cycles represent a fundamental difference in the way heterozoan carbonates aggrade in shallow, low-energy systems in comparison to those formed in higher-energy, open shelf settings.